Kara Goucher of Portland was 10th in 30:55.16. Amy Yoder Begley of Beaverton was 26th in 32:38.28.
Dibaba, the two-time 10,000 world champion, sat just behind Turkey's Elvan Abeylegesse until the start of the last lap, then went to the front with 350 meters to go.
She surged ahead down the back stretch and finished almost two seconds clear of Abeylegesse, who took silver in 29:56.34. The pair were only the second and third women to break the 30-minute barrier.
Wang Junxia of China set the world record of 29:31.78 in 1993.
Shalane Flanagan set a U.S. record 30:22.22 to win bronze.